How Cement & Concrete are Made
Cement is the essential ingredient in concrete. Cement is a powder that — when mixed with water, sand, and aggregates — produces concrete. Cement typically represents 7% to 11% of a concrete mix and acts as the glue that holds concrete together. The cement making process can be divided into two basic steps:
Clinker production: Clinker is an intermediate product in cement manufacturing and is the main substance in cement. Clinker is made in a rotary kiln at temperatures of 1470°C.
Contempra cement— a new cement that reduces CO2 emissions by up to 10% by intergrinding regular clinker with up to 15% limestone (10% more than in regular Portland cement) — uses less clinker, thereby reducing the amount of greenhouse gas emissions.
Grinding: The clinker is then ground with other minerals to produce the powder we know as cement. Cement is mostly used to make concrete and concrete is always manufactured to meet the specific requirements of each construction project.
The basic components of concrete are sand and gravel (fine and coarse aggregate), cement to glue them together, and water. Chemicals — called admixtures — are sometimes added during the concrete production stage to trap air, remove water, change the viscosity, and alter other performance properties. Producers enhance the bonding process of cement at the concrete production stage with supplementary cementing materials (SCMs), which come from industrial waste streams.
Cement manufacturing is an energy-intensive process and results in the unavoidable release of CO2 emissions — 60% of which occurs during the clinker production phase, with each tonne of clinker generating 525 kg of CO2 due to the calcination process.
The Canadian cement and concrete industry is pursuing a variety of innovative measures to further reduce its carbon footprint. These measures include: the use of alternative and renewable energy sources to reduce reliance on fossil fuels, the increased use of supplementary cementing materials to partially replace clinker, and potentially transformative technologies such as carbon capture and reuse.